1. Technical Field of the Invention
The present invention relates generally to a sequentially joined-segment coil of a rotary electric machine and a production method thereof which ensures a high degree of electrical insulation and allows decreases in size and weight thereof.
2. Background Art
Sequentially joined-segment stator coils have been proposed which are made by conductor segments inserted in slots in a stator core whose ends are joined in sequence. For instance, Japanese Patent No. 3118837 (U.S. Pat. No. 6,249,956), assigned to the same assignee as that of this application, discloses a production method of joining U-shaped conductor segments in sequence to make a stator coil.
The sequentially joined segment stator coil, as taught in the above patents, is made by inserting a pair of legs of each conductor segment into two of slots of a core located at an interval away from each other which is substantially equivalent to a magnetic pole pitch of a rotor, bending end portions of the legs projecting from the slots in a circumferential direction of the core, and joining the end portions of the conductor segments in series.
The conductor segments each consist of a U or V-shaped head (also called a turn), a pair of side conductor portions extending from the head to be inserted into two of the slots of the core from an axial direction of the core, and end portions which project from the side conductor portions toward the other side of the slots and extend in the circumferential direction of the core. The projecting end portions are joined in pair. In the following discussion, the side conductor portion and the projecting end portion will also be referred to as a leg as a whole, the heads of the conductor segments will also be referred to as a segment head-side coil end of the stator coil, and the projecting end portions will also be referred to as a segment end-side coil end of the stator coil.
Japanese Patent Publication No. 3118837 (U.S. Pat. No. 6,249,956) also discloses a method of forming slant portions of a head of each of a small-sized conductor segment and a large-sized segment. The formation of the slant portions is achieved by fitting a total of four legs of a set of the small-sized conductor segment and the large-sized segment extending over the small-sized segment within two rings arrayed coaxially with each other and rotating the rings in opposite directions to spread the legs in circumferential directions of the rings.
Japanese Patent First Publication No. 2000-139049 (U.S. Pat. No. 6,177,747) discloses a method of forming the slant portions of the head of each conductor segment which is achieved by fitting a total of four legs of a set of the small-sized conductor segment and the large-sized segment extending over the small-sized segment within four rings arrayed coaxially with each other and rotating the rings in opposite directions to spread the legs of each conductor segment in circumferential directions of the rings.
Japanese Patent No. 3104700 (U.S. Pat. No. 6,403,921) discloses welding two of tips of end portion of conductor segments arrayed adjacent to each other in the radius direction of a stator core and teaches use of a restraint member which is disposed between the adjacent two of the tips to secure a desired orientation of the welded tips.
Japanese Patent No. 3118837 (U.S. Pat. No. 6,249,956) discloses bending a conductor bar through 180xc2x0 to produce a U-shaped segment. Japanese Patent First Publication No. 2001-245446 teaches bending wire 180xc2x0 many times to make the same coil as the above described sequentially joined-segment stator coil. This type of stator coil eliminates the need for a welding process, but requires use of a stator coil with open slots indispensably.
Japanese Patent Fist Publication No. 2000-92766 (U.S. Pat. No. 6,201,332) discloses a sequentially joined-segment stator coil in which six legs of conductor segments are aligned within each slot of a stator core in a radius direction of the stator core.
An example of the production methods of the sequentially joined-segment stator coil as taught in the above publications will be discussed below in detail.
First, a required number of pine needle-like conductor segments are prepared. Each of the conductor segments is formed into a U-shape one with side conductor portions extending at substantially a magnetic pole pitch interval away from each other. The side conductor portions of each conductor segment are placed spatially in alignment with two of the slots formed in the core, respectively, (i.e., in a circumferential direction of the core) for simultaneous insertion of the side conductor portions into the slots. These steps may be achieved with a pair of coaxially arrayed rings with slots, as illustrated in FIG. 3 of Japanese Patent No. 3118837. Specifically, legs of each conductor segment are fitted in two of the slots aligned in a radius direction of the rings. Next, the rings are turned relative to each other through a given angle equivalent to a magnetic pole pitch to spread the legs, thereby forming the U-shaped conductor segment.
Subsequently, the head of each of the U-shaped conductor segments is held. The legs are drawn from the slots and then inserted into the slots of the core.
Next, end portions of the legs projecting from the slots are bent in the circumferential direction of the core through half a magnetic pole pitch. Such bending may be achieved with a plurality of coaxially arrayed rings with slots, as illustrated in FIGS. 4 and 5 of Japanese Patent No. 03196738. Specifically, tips of the projecting end portions of the legs are inserted into the slots of the rings. The rings are rotated in the circumferential direction by half a magnetic pole pitch (i.e., an electrical angle of xcfx80/2) to bent the projecting end portions in the circumferential direction through half the magnetic pole pitch. It is advisable that the rotation of the rings be performed while urging the rings toward the projecting end portions (i.e., the axial direction of the core) for increasing the radius of curvature of the turn of each conductor segment. Next, the projecting end portions are welded in a given sequence, thereby forming an endless phase coil. Any one of the heads of the U-shaped conductor segments is cut to define coil terminals. If the coil terminals are made longer and bent in the circumferential direction, they may be employed as a neutral point connecting line. The reason that the coil terminals are provided in the segment head-side coil end is because if the coil terminals are provided in the segment end-side coil end, they will interface with welding of the end portions of the conductor segments.
The above sequentially joined-segment stator coil is usually employed as a stator coil of automotive ac generators and has suffered from the following drawback.
Each of the pine needle-like conductor segments for use in making the U-shaped conductor segment has the 180xc2x0 bent head which is greater in width than a total width of legs of each of the conductor segments because the head is bent with a certain curvature. This increases the damage to insulating coatings on the heads of the conductor segment. The problems is also encountered by the multi-bend coils as taught in Japanese Patent First Publication No. 2001-245446.
Typically, the legs of each of the conductor segments are placed within one of slots of the stator core at different locations aligned in the radius direction of the stator core. Alternatively, the set of the large-sized and small-sized conductor segments has a total of four legs disposed within one of the slots at four adjacent locations.
Usually, electric motors used to drive automotive vehicles is supplied with power from a high-voltage battery. It is, thus, very difficult to decrease the curvature of the heads of the conductor segments as compared with typical automotive ac generators, which results in a great increase in diameter of the segment head-side coil end of the stator coil made up of the heads of the conductor segments.
The segment head-side coil end of the conventional sequentially joined-segment stator coils has some of the conductor segments arrayed in the radius direction of the stator core, so that a pitch between portions of the conductor segments at the segment head-side coil end will be greater than a radius-wise width of the tips of the heads of the conductor segments. In a case of electric motor used to drive automotive vehicles, a given clearance is preferably provided between adjacent two of the heads of the conductor segments for ensuring the electrical insulation of the stator coil.
For the reasons as described above, the pitch between portions of the conductor segments placed within each slot of the stator core must be equal to the pitch between the tips of the heads of the conductor segments, thus resulting in a decreased slot space factor of the stator core and an increased diameter of the stator core which leads to increases in size and weight of the motor.
It is therefore a principal object of the invention to avoid the disadvantages of the prior art.
It is another object of the invention to provide a sequentially joined-segment stator coil for a rotary electric machine which is designed to ensure a desired degree of electrical insulation of a segment head-side coil end of the stator coil and capable of decreasing the size and weight thereof and a production method thereof.
According to one aspect of the invention, there is provided a sequentially joined-segment stator coil which may be employed in a rotary electrical machine such as an electrical motor. The stator coil comprises: (a) a stator core having opposed ends and slots formed at given intervals in a circumferential direction of the stator core, each of the slots defining therein even segment-inserted is positions which are aligned in a radius direction of the stator core; and (b) a plurality of segments placed in the slots of the stator core, the segments being joined in sequence to form turns of each of M (=an integer more than two) phase coils. Each of the segments includes a pair of conductor portions each of which is inserted into one of two of the slots spaced from each other at a given interval, a head portion extending from the pair of conductor portions outside one of the ends of the stator core to form a segment head-side coil end, and a pair of end portions each of which extends from one of the pair of conductor portions outside the other end of the stator core to form a segment end-side coil end. Each of the head portions is made up of a substantially U-shaped tip portion and a pair of slant portions which continue from ends of the head portion, slant to a circumferential and an axial direction of the stator core, and lead to the conductor portions, respectively. Each of the end portions is made up of slant end portions slanting from the two of the slots to the circumferential and axial directions and tips each of which continues from one of the slant end portions and is joined to one of the tips of the end portions of another of the segments. The segment head-side coil end includes a plurality of sets of the head portions arrayed in the radius direction of the stator core, as viewed in the circumferential direction of the stator core. The segment end-side coil end includes a plurality of sets of the end portions arrayed in the radius direction, as viewed in the circumferential direction of the stator core.
Each of the tip portions of the head portions of the segments bulges more than a corresponding one of the pairs of conductor portions in the radius direction of the stator core. A radius-wise pitch between two of the tip portions adjacent to each other in the radius direction is greater than a width of the tip portions in the radius direction. A radius-wise pitch between the slant portions of two of the head portions arrayed adjacent to each other in the radius direction of the stator core is smaller than the width of the tip portions in the radius direction.
Specifically, the radius-wise pitch between the two of the tip portion is greater than the width of the tip portion and the radius-wise pitch between the slant portions. This geometry is established by increasing the pitch of the slant portions as getting away from the end of the stator core. This allows a desired number of turns of the stator coil to be installed within a motor housing without increasing the diameter of the stator core and provides a desired degree of electrical insulation of the segment head-side coil end of the stator coil. Additionally, the increase in interval between the slant portions of the head portions facilitates flow of cooling air passing through the slant portions, thus resulting in greatly improved cooling capability of the stator coil.
The segments may be made up of two types: a large-sized segment and a small-sized segment. The conductor portions of each of the small-sized conductor segments may be placed at two different locations defined adjacent to each other in the radius direction of the stator core. The conductor portions of each of the large-sized conductor segments may be placed at two different locations provided inside and outside of the locations of the conductor portions of the small-sized segment. In this case, each of the small-sized segments and one of the large-sized segments may be viewed in the circumferential direction of the stator core as a segment set. The same beneficial effects may also be obtained if each of the segment as referred to in the above stator coil is considered as the segment set.
The above described arrangements of the segments may be used with the multi-bend coils as taught in Japanese Patent First Publication No. 2001-245446.
In the preferred mode of the invention, the radius-wise pitch between the adjacent two head portions at the slant portions thereof increases as getting away from the end of the stator core in an axial direction of the stator core. Outside ones of the pairs of slant portions of the head portions in the radius direction of the stator core lean outwardly at an angle to an axial direction of the stator core which is greater than that of inside ones of the slant portions. The outward leaning of the slant portions causes the pitch between the conductor portions to be increased, thus facilitating ease of manufacture.
The radius-wise pitch between the adjacent two head portions at the slant portions thereof increases as getting away from the end of the stator core in an axial direction of the stator core. Inside ones of the pairs of slant portions of the head portions in the radius direction of the stator core may alternatively lean inwardly at an angle to an axial direction of the stator core which is greater than that of outside ones of the slant portions.
The slant portions of the head portions may be bent or curved in the radius direction of the stator core.
The segments is broken down into a plurality of segment sets each made up of a small-sized segment with a small head and a large-sized segment with a large head extending over the small head of the small-sized segment in the circumferential direction of the stator core. The segment sets is broken down into a plurality of segment set groups arrayed in the radius direction of the stator core. The segment sets in each of the segment set groups are arrayed in the circumferential direction of the stator core. Each of the segment set groups forms partial phase windings to which given phase voltages are applied, respectively. Each of the phase coils includes ones of the partial phase windings which are arrayed in the radius direction of the stator core and joined in series. The slots are broken down into same phase slot groups each of which has placed therein the conductor portions of the segments to which the same phase voltage is applied. The slots in each of the same phase slot groups is arrayed adjacent to each other in the circumferential direction of the stator core. The partial phase windings arrayed in the radius direction of the stator core within each of the slots of each of the same phase slot groups are joined in series to form a series-connected phase coil circuit The series-connected phase coil circuits placed respectively within the slots of each of the same phase slot groups are joined in parallel to form each of the phase coils.
According to the second aspect of the invention, there is provided a sequentially joined-segment stator coil for a rotary electrical machine which comprises: (a) a stator core having opposed ends and slots formed at given intervals in a circumferential direction of the stator core, each of the slots defining therein even segment-inserted positions which are aligned in a radius direction of the stator core; and (b) a plurality of segments placed in the slots of the stator core, the segments being joined in sequence to form turns of each of M (=an integer more than two) phase coils. Each of the segments includes a pair of conductor portions each of which is inserted into one of two of the slots spaced from each other at a given interval, a head portion extending from the pair of conductor portions outside one of the ends of the stator core to form a segment head-side coil end, and a pair of end portions each of which extends from one of the pair of conductor portions outside the other end of the stator core to form a segment end-side coil end. Each of the head portions is made up of a substantially U-shaped tip portion and a pair of slant portions which continue from ends of the head portion, slant to a circumferential and an axial direction of the stator core, and lead to the conductor portions, respectively. Each of the end portions is made up of slant end portions slanting from the two of the slots to the circumferential and axial directions and tips each of which continues from one of the slant end portions and is joined to one of the tips of the end portions of another of the segments. The segment head-side coil end includes a plurality of sets of the head portions arrayed in the radius direction of the stator core, as viewed in the circumferential direction of the stator core. The segment end-side coil end includes a plurality of sets of the end portions arrayed in the radius direction, as viewed in the circumferential direction of the stator core.
Each of the tip portions of the head portions of the segments bulges more than a corresponding one of the pairs of conductor portions in the radius direction of the stator core. A radius-wise pitch between two of the tip portions adjacent to each other in the radius direction is smaller than a width of the tip portions in the radius direction. Sections of the tip portions having a maximum width in the radius direction of the stator core are shifted in location from each other in the axial direction of the stator core.
Specifically, the bulges of the tip portions of the segments are shifted in the axial direction of the stator core, that is, the lengthwise direction of the segments, thereby eliminating physical interference between adjacent two of the bulges, which results in a decrease in pitch between the conductor portions placed within each of the slots.
Each of the segments, like the above, may be viewed as the segment set.
In the preferred mode of the invention, two of the tip portions of the head portions arrayed adjacent to each other in the radius direction of the stator core are shifted from each other in the axial direction of the stator core a distance longer than a length of the tip portions in the axial direction of the stator core.
The segments are broken down into a plurality of segment sets each made up of a small-sized segment with a small head and a large-sized segment with a large head extending over the small head of the small-sized segment in the circumferential direction of the stator core. The segment sets are broken down into a plurality of segment set groups arrayed in the radius direction of the stator core. The segment sets in each of the segment set groups are arrayed in the circumferential direction of the stator core. Each of the segment set groups forms partial phase windings to which given phase voltages are applied, respectively. Each of the phase coils includes ones of the partial phase windings which are arrayed in the radius direction of the stator core and joined in series.
The slots are broken down into same phase slot groups each of which has placed therein the conductor portions of the segments to which the same phase voltage is applied. The slots in each of the same phase slot groups are arrayed adjacent to each other in the circumferential direction of the stator core. The partial phase windings arrayed in the radius direction of the stator core within each of the slots of each of the same phase slot groups are joined in series to form a series-connected phase coil circuit. The series-connected phase coil circuits placed respectively within the slots of each of the same phase slot groups are joined in parallel to form each of the phase coils.
According to the third aspect of the invention, there is provided a sequentially joined-segment stator coil of a rotary electrical machine which comprises: (a) a stator core having opposed ends and slots formed at given intervals in a circumferential direction of the stator core, each of the slots defining therein even segment-inserted positions which are aligned in a radius direction of the stator core; and (b) a plurality of segments placed in the slots of the stator core, the segments being joined in sequence to form turns of each of M (=an integer more than two) phase coils. Each of the segments includes a pair of conductor portions each of which is inserted into one of two of the slots spaced from each other at a given interval, a head portion extending from the pair of conductor portions outside one of the ends of the stator core to form a segment head-side coil end, and a pair of end portions each of which extends from one of the pair of conductor portions outside the other end of the stator core to form a segment end-side coil end. Each of the head portions is made up of a substantially U-shaped tip portion and a pair of slant portions which continue from ends of the head portion, slant to a circumferential and an axial direction of the stator core, and lead to the conductor portions, respectively. Each of the end portions is made up of slant end portions slanting from the two of the slots to the circumferential and axial directions and tips each of which continues from one of the slant end portions and is joined to one of the tips of the end portions of another of the segments. The segment head-side coil end includes a plurality of sets of the head portions arrayed in the radius direction of the stator core, as viewed in the circumferential direction of the stator core. The segment end-side coil end includes a plurality of sets of the end portions arrayed in the radius direction, as viewed in the circumferential direction of the stator core.
Each of the tip portions of the head portions of the segments bulges more than a corresponding one of the pairs of conductor portions in the radius direction of the stator core. A radius-wise pitch between two of the tip portions adjacent to each other in the radius direction is smaller than a width of the tip portions in the radius direction. Sections of the tip portions having a maximum width in the radius direction of the stator core are shifted in location from each other in the circumferential direction of the stator core.
Specifically, the bulges of the tip portions of the segments are shifted in the circumferential direction of the stator core, that is, the widthwise direction of the segments, thereby eliminating physical interference between adjacent two of the bulges, which results in a decrease in pitch between the conductor portions placed within each of the slots.
Each of the segments, like the above, may be viewed as the segment set.
In the preferred mode of the invention, two of the tip portions of the head portions arrayed adjacent to each other in the radius direction of the stator core are shifted from each other in the circumferential direction of the stator core a distance longer than a length of the tip portions in the circumferential direction of the stator core.
The segments are broken down into a plurality of segment sets each made up of a small-sized segment with a small head and a large-sized segment with a large head extending over the small head of the small-sized segment in the circumferential direction of the stator core. The segment sets are broken down into a plurality of segment set groups arrayed in the radius direction of the stator core. The segment sets in each of the segment set groups are arrayed in the circumferential direction of the stator core. Each of the segment set groups forms partial phase windings to which given phase voltages are applied, respectively. Each of the phase coils includes ones of the partial phase windings which are arrayed in the radius direction of the stator core and joined in series.
The slots are broken down into same phase slot groups each of which has placed therein the conductor portions of the segments to which the same phase voltage is applied. The slots in each of the same phase slot groups are arrayed adjacent to each other in the circumferential direction of the stator core. The partial phase windings arrayed in the radius direction of the stator core within each of the slots of each of the same phase slot groups are joined in series to form a series-connected phase coil circuit. The series-connected phase coil circuits placed respectively within the slots of each of the same phase slot groups are joined in parallel to form each of the phase coils.
Typical sequentially joined-segment stator coils are usually employed as automotive ac generator, but however, now expected to be used for automotive high power drive motors to produce torque to drive an automobile. It is necessary to supply an extremely high voltage (e.g., a few hundred voltages) to such drive motors in order to compensate for a loss thereof caused by resistances of wiring and the stator coil. However, service speeds of the both are substantially identical, thus requiring the sequentially joined-segment stator coil for the automotive drive motor to have turns greater in number than the one for the automotive ac generator. The increase in turns may be, as shown in FIG. 16, by laying segments 33a, 33b, 33c, 33d, and 33e to overlap each other to increase conductor portions arrayed in the slot S in a radius direction of the stator core 1. This multi-lap segment structure, however, encounters drawbacks that types of segments needs to be increased with an increase in lap of the segments, and a head of an outermost one of the segments has a greater length, thus resulting in an increase in electrical resistance thereof.
Particularly, although not illustrated clearly in FIG. 16, the width of the tip H of each segment is commonly greater than that of legs L thereof for production reasons. This causes the width W of the segment head-side coil end 311 of the stator coil to be great and also the distance of the segment head-side coil end 311 projecting from an end of the stator core 1 to be great, thus resulting in an increase in overall size and weight of the stator coil.
Additionally, the multi-lap segment structure also has drawbacks in that the greater width of the tips H of the segments results in a great degree of rubbing thereof, and the clearance d between adjacent two of the legs H of the segments needs to be increased for avoiding the rubbing, which results in a decrease in space factor of the stator coil and that the laps of the segments lead to the deterioration in heat dissipation from the segment 33a. 
In order to avoid the above problems, in the sequentially joined-segment stator coil, as described above, each set of the large-sized and small-sized segments has legs disposed, as shown in FIG. 3, in adjacent four of the slots arrayed in the radius direction of the stator core 1. The segment sets arrayed in the circumferential direction of the stator core 1 are joined in series to form each of the partial phase windings. The partial phase windings arrayed adjacent each other in the radius direction of the stator core 1 are joined in series to form each of the phase coils.
According to the fourth aspect of the invention, there is provided a production method of the sequentially joined-segment stator coil as described above. The method comprises: (a) preparing conductor segments each including a head and a pair of legs extending from ends of the head; (b) preparing a plurality of rings arrayed coaxially with each other to be rotatable relative to each other; (c) holding portions of the legs of each of the conductor segments in the rings, respectively, which make the conductor portions placed in the stator core; (d) leaning the heads of the conductor segments outwardly of the rings simultaneously; and (e) rotating the rings to spread end portions of each of the heads of the conductor segments to complete the slant portions of a corresponding one of the head portions of the segments.
In the preferred mode of the invention, the method further comprises preparing a head press member having formed therein a frusto-conical protrusion to define a tapered peripheral surface. The leaning of the heads of the conductor segments is achieved by moving the head press member toward the rings in an axial direction of the rings to press an inner one of the end portions of each of the heads of the conductor segments outwardly in the radius direction of the rings through the tapered peripheral surface.
The method further comprises a cylindrical stopper member working to stop the leaning of the heads of the conductor segments for avoiding an excessive inclination of the heads.
The conductor segments are broken down into a plurality of segment sets each made up of a small-sized conductor segment with a small head and a large-sized conductor segment with a large head extending over the small head of the small-sized conductor segment. The stopper member works to hold the small-sized head of each of the small-sized conductor segment from moving outside the large-sized head of the large-sized conductor segment in the radius direction of the rings.